A cylinder lock includes a cylinder or plug rotatably disposed within a bore formed in a shell or housing. A keyway formed axially in the plug accepts a key having a blade shaped and warded to correspond to grooves and ridges of the keyway. Rotation of the cylinder within the shell may be controlled by one or more tumbler pin assemblies, whereby bitting formed on the key blade elevates each tumbler pin assembly to align the assembly with the shear line between the cylinder and the shell to enable the cylinder to rotate. As an alternative to tumbler pins or in addition to tumbler pins, a sidebar may be disposed in the cylinder and configured for radial movement relative to the cylinder. The sidebar includes knife edge that, when the sidebar is radially extended with respect to the cylinder, extends into an axial groove formed in the wall of the shell bore to prevent rotation of the cylinder. A slider is disposed within the cylinder and includes a sidebar-blocking portion that engages a corresponding portion of the sidebar to prevent the sidebar from moving radially inwardly and retracting from the axial groove. The slider includes a portion that extends into the keyway, and a properly configured key will contact the slider and, as the key is inserted into the keyway, will move the slider into a position whereby the corresponding blocking portions of the slider and the sidebar are not engaged, thereby enabling the sidebar to move radially inwardly to withdraw from the axial groove and permit the cylinder to rotate.
Exemplary locks and associated keys having various configurations of tumbler pins, sidebars, and sliders are described in U.S. Pat. Nos. 6,477,875; 6,945,082; and 7,797,973, the respective disclosures of which are hereby incorporated by reference.